Transmural myocardial infarction was identified in six patients with hypertrophic cardiomyopathy and normal coronary arteries. Transmural myocardial infarct presented as sudden death, classical infarct or was silent. While left ventricular dilatation is rare in hypertrophic cardiomyopathy, one of the factors predisposing to this unusual feature appears to be transmural myocardial infarction.